Here is the Federal Railroad Administration's No. 217 Office of Safety vehicle AKA Track Geometry car. I did not know of it's existence. It is seen here on Amtrak's National Train Day, May 8, 2010... (more)
FRA track geometry train glides along inspecting tracks from Decatur to Mattoon. This self-propelled car holds up to 20 people, has a computer room and a kitchen.